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Inside AZGFD
 
Water Management
 

Arizona has been under drought conditions for several years. Despite an abnormally wet winter in 2005 and a seemingly average-to-above-average 2006 summer monsoon, long term drought conditions still persist across the region with multi-year precipitation deficits to overcome. It should be noted that even in years where annual precipitation is close to normal, it may be the result of concentrated rainfall during one month, following many hot summer months with no measurable precipitation at all.  Severe drought conditions in 1996 and 2002 were likely causes for the bighorn population dips observed on the 1997 and 2003 aerial population surveys. 

Water developments are an important wildlife management tool in the southwest.  The vast majority of research indicates that water distribution is a critical habitat variable for desert bighorn, especially during summer months when temperatures can reach 120°F.  Desert bighorn can sometimes survive on preformed water found in their food and metabolic water formed by oxidative metabolism. During summer bighorn may go without water for five to 15 days, resulting in a loss of more than 20% of the hydrated body weight.  During this time however, increased day length, extreme ambient temperatures, reduced moisture content of forage, and mating activities necessitate additional water intake, and thus a dependence on reliable water sources .

The Kofa NWR has a large number of water sources but their utility for sheep and their reliability varies greatly.  Table 1 is a list of waters considered to be critical to bighorn sheep, based on their locations in sheep habitat and documentation of sheep use from waterhole counts, aerial surveys, and remote cameras.  

Table 1:  Critical bighorn sheep waters on the Kofa and recommended management actions

Name

Type of Water

Management Unit

Suggested maintenance/management action

Cereus Tank†

Developed tinaja

45A

Vehicle water supplementation, evaporative cover

High Tank 8

Developed tinaja

45A

Supplementation not expected in 2007

High Tank 2 Spring

Developed spring

45A

Supplementation not expected in 2007

Maggot Tank†

Tinaja

45A

Helicopter water supplementation, evaporative cover

Hidden Valley Tank†

Developed tinaja

45A

Vehicle water supplementation, evaporative cover

Tunnel Springs

Developed spring

45A

Supplementation not expected in 2007

High Tank 6

Developed tinaja

45A

Vehicle water supplementation, evaporative cover

Frenchman Tank†

Developed tinaja

45B

Helicopter or vehicle supplementation TBD, evaporative cover

Yaqui Tank†

Developed tinaja

45B

Vehicle water supplementation, evaporative cover
Redeveloped in 2007

White Dike (High Tank 3)†

Developed tinaja

45B

Helicopter water supplementation, evaporative cover

Charlie Died*

Buried system

45B

Vehicle water supplementation

Moonshine Tank†

Developed tinaja

45B

helicopter water supplementation, slated for redevelopment

Old Moonshine Tank†

Tinaja

45B

helicopter water supplementation, evaporative cover installed

Adam’s Well*

Well

45C

Supplementation not expected in 2007

Horse Tank*

Developed tinaja

45C

Vehicle water supplementation

Black Tank*

Developed tinaja

45C

Vehicle water supplementation

Little White Tanks*

Developed tinaja

45C

Vehicle water supplementation

Saguaro Tank†

Developed tinaja

45C

Helicopter water supplementation, evaporative cover

Modesti Tank

Buried system

45C

Vehicle water supplementation

Chain Tank*

Developed tinaja

45C

Supplementation not expected in 2007

Burnt Wagon Tank

Tinaja

45C

Supplementation not expected in 2007, evaporative cover

McPherson Tank

Tinaja

45C

Redeveloped in 2007

Livingston Hills

New temporary water

45A

New water development

Engesser Pass

New temporary water

45B

New water development

*Tank in wilderness, supplementing water covered by CCP or other documentation
†Tank in wilderness, MRA needed prior to water supplementation

Few of the bighorn waters could be considered permanent, which means that they may go dry during the height of summer when water is needed most, or during drought years.  A special water survey was conducted on June 1 of the severe drought year of 1996 and very few of the known waterholes were not dry.  In addition to bighorn that may have succumbed to dehydration or malnutrition, about 20 bighorns were found to have died after becoming entrapped in tinajas (so-called “death traps”) with greatly lowered water levels.  No similar water survey was conducted during the extreme drought year of 2002.  If a water source dries up, bighorn may not move to new areas to find water.  It is not always known if some remote waters go dry because many are not checked regularly.  Bighorn populations in surrounding hunt units, where Arizona Game and Fish has maintained waters, have remained fairly stable in comparison to the Kofa population, where only a few easily accessible waters are maintained.  Kofa NWR waters predate wilderness designation on the refuge, and for many of these waters their maintenance by vehicle or helicopter is covered under existing management plans, or MRAs.  During years of severe drought, the refuge has hauled water to Black, Charlie Died, Figueroa, Horse, Little White, and Modesti Tanks, and De La Osa Well.  These waters are accessible by vehicle.  In 2006, water was hauled to Black, Modesti, and Little White Tanks.  The development and use of new methods for reducing evaporation from waterholes include floating surface covers that reduce the amount of surface area exposed while still allowing animals to drink.  This method may be used at existing waters without shade covers and could reduce the need for water hauling.  Some existing waters may be modified so that water levels can be easily monitored from the air.  Table 2 (below) describes what management actions should be taken to ensure designated critical waters remain full and available to sheep throughout the summer.

Objective: Ensure year-round water availability for all bighorn sheep on the Kofa NWR.

Strategy:  Identify priority waters that will have water maintained at all times.  This will likely require hauling water into remote locations during dry times, sometimes with the use of a helicopter. Evaporation-reducing floating covers may also be installed.

Strategy:  Identify existing waters that need to be redeveloped to improve water holding capacity and efficiency.  Solicit funding and volunteer labor to accomplish the projects.

Strategy: Formalize maintenance and monitoring procedures at all water sources via development and implementation of a refuge water protocol.

Strategy: Identify locations for additional water sources and begin the planning process to construct them. Use and monitor temporary water containers to test effectiveness and actual sheep use of a new water before it is constructed.

Strategy: Enlist volunteers to assist the refuge with water development monitoring and maintenance.

 

Table 2

In addition to a need for better monitoring and maintenance of existing waterholes, a better distribution of permanent water supplies is needed to provide water in all areas of suitable sheep habitat.  Some areas of habitat that could support sheep do not currently have water sources, or existing water sources are non-functional, potentially rendering that patch of habitat unavailable for sheep.  Some existing ephemeral waters can be improved or redeveloped to hold water longer, but in some areas new waters might need to be built.  The 1996 Refuge and Wilderness Plan does not specifically reference the construction of new waters in wilderness, but does mandate the Fish and Wildlife Service to “manage wilderness portions of the planning area using the minimum tools needed for maintaining an optimal desert bighorn sheep population . . .”  New water developments can likely be constructed outside of wilderness, although construction in wilderness should remain an option if a wilderness location best meets wildlife management needs.  Installation and monitoring of temporary waters can be used to determine if a selected water site will be used by bighorn sheep before a permanent structure is built.  Redevelopment of older waters might reduce impacts to wilderness by reducing or eliminating the need for water hauling and reducing visual impacts because new developments are less obtrusive than old ones (Figure 2,) which often contain concrete dams or shades that could be removed after redevelopment. Figure 2 shows the redeveloped Charlie Died Tank and juxtaposes the buried redeveloped tank with the previous modified natural tinaja.


Figure 2:  Charlie Died Tank on Kofa NWR illustrating old (background) and
new-style (foreground) wildlife waters

Most bighorn habitat models use proximity to a permanent water source as a criterion to rank habitat quality; however opinions vary as to the maximum distance between water sources.  Turner et al. (2004) found that 97% of desert bighorn collar locations were within 1.86 miles of water.  Some consider the highest ranking habitat to be within two miles of a permanent water source, while other researchers found desert bighorn up to three miles from water.  Figure 3 provides a graphical portrayal of water availability within a three mile radius of permanent waterholes on the refuge.  Plans for major water renovations or new water developments will require an environmental assessment and minimum requirement analysis/minimum tool analysis.  Construction of new waters and redevelopment of existing waters can be done using new techniques that place most of the structures underground, greatly reducing the visual impact of the site.

Figure 3:  Bighorn sheep waters with 3-mile radius circle drawn around “permanent”waterholes (red dots).  Habitat outside circles lacks adequate water supplies. Green and blue dots are bighorn locations from fall surveys 1992-2003.


 

   

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